Interpretive Summary: Beekeepers must use a control method in their colonies because of the presence of two parasitic mites in honey bees. The most common controls are several pesticides that kill the mites but not adult bees. However current problems with queens that do not perform well in colonies may be due to residues of the pesticides that are absorbed by the wax comb. By exposing developing queens to known levels of the pesticide, coumaphos, we determined that 1000 ppm prevented larvae from developing into queens, 100 ppm reduced the numbers of queens by 50% and these queens were lighter in weight. When conditions were stressful (very hot and dry), queens exposed to pesticide during rearing were slower to begin egg laying and many mated with fewer drones. For all queens reared successfully, survival in colonies for six months was not different between the several treatment levels. This information will help beekeepers manager their hives.

Technical Abstract:
Young honey bee larvae were transferred into wax queen cups containing known concentrations (0 to 1000 ppm) of the organophosphate coumaphos. These larvae were placed in queenless colonies and examined ten days later to determine the rate of acceptance as indicated by a mature sealed queen cell. All but one queen failed to develop at 1000 ppm, and more than 50% of the queen cells were rejected at the 100 ppm concentration. Additionally, queens that survived exposure to100 ppm coumaphos weighed significantly less than control queens. The sublethal effects of coumaphos on developing queens were also investigated. Mature queen cells from the same treatments were placed in small mating colonies for 21 days. Then the queens were collected after being rated for quality. The queens were either introduced to production colonies and monitored for six months or dissected to determine mating success. The queens that had been exposed to the 100 ppm coumaphos during rearing were more susceptible to stress. During an exceptionally hot, dry summer, many of these queens failed to lay eggs within 21 days and a greater percentage of them mated poorly. The rate of loss over six months for queens introduced to production colonies was not statistically different between treatments.